When pedaling a bicycle in a normal manner with the rider's shoes not attached to the pedals, the pedaling force to rotate the bicycle drive wheel is only provided during about half the 360.degree. of movement of each pedal. That is, first one pedal is providing the basically downward thrust to rotate the pedal sprocket while the other pedal is moving upward without any driving force being provided, then the situation is reversed as the other pedal is moved downward. These alternating forces by the opposite pedals are satisfactory for much bicycling activity. However, it is well known that it is much more efficient to propel a bicycle if each pedal is providing thrust throughout the entire 360.degree. of rotation for each of the pedals.
Bicycle racers as well as some recreational bicyclists attach their shoes to the pedals to enable the application of force throughout the entire 360.degree. rotation. There are two main methods for attaching the shoes to the pedals. The most common approach is to use a toe clip and strap which cups the toe of the show and straps it to the pedal. Often a cleat is also used to prevent the shoe from sliding rearwardly out of the toe clip. A newer connecting arrangement incorporates a quick release type of tab and groove or cleat and pedal system. In this system the bottom portion of the shoe contains either tabs, grooves or a cleat which mate with corresponding grooves, tabs or cleat coupling structure, respectively, mounted on the bicycle pedal. This system allows for quick secure attachment to a pedal without the encumbrance of the traditional toe clip and strap system which requires loosening the toe clip strap for pedal entry and tightening the strap for a secure fit and optimum pedaling efficiency. With the quick release binding system, the rider merely twists or slides his or her foot in or out of the pedal for secure fastening without the use of a toe clip.
In order to assure maximum pedaling efficiency throughout the 360.degree. rotation of the bicycle pedal, and also to assure a secure connection between the outsole and the pedal, the outsole plates of cycling shoes used in quick-release cleat and pedal systems are frequently formed of a rigid material. In order to assure comfort to the foot overlying such a rigid outsole plate, the outsole plate is frequently contoured to approximately follow the bottom of a typical foot in the area of the ball of the foot. The outsole is thus curved. The curvature of the outsole in the area of the ball of the foot inhibits the ability of mounting cleats in a manner that maximizes both pedaling efficiency and safety. That is, it is desirable to position a cleat to the medial side of the shoe from both the pedaling efficiency standpoint and the safety standpoint. In order to prevent an injury from contact with the bicycle frame, it is desirable to position the feet on the pedal a distance away from the bike frame. In order to maximize pedaling efficiency, it is desirable to apply pedaling force at approximately the first metatarsal head. It is thus desirable to locate the center of a cycling cleat about the first metatarsal head cleat. However, such off-center positioning of a cleat can result in the cleat extending past the medial border of the outsole plate. Such an unsupported portion of the cleat results in instability, and defeats the purpose of enhancing pedal efficiency. Cyclists frequently use shims or wedges between the curved bottom of the outsole plate and the cleat in an attempt to provide additional support and stability to the off-center positioned cleat. The curved bottom of the outsole plate follows the curvature of the foot, and thus the arc of the curve changes from small to large shoe sizes, with the arcs in the smaller sizes having a smaller radius of curvature. The smaller arc of the sole in small shoe sizes requires that the curved portion be thicker in order to retain rigidity, thus adding additional weight.
It is also desirable, for safety purposes, to allow a limited degree of rotatability for the foot during pedaling in order to relieve stresses on the ankle and knee joints. Again, the typical curvature of a rigid outsole cycling plate makes it difficult to address this safety concern since rotatability of the cleat cannot be provided for along the curved outsole plate. This problem has been addressed in pedal designs wherein limited rotatability is provided between the cleat and the bicycle pedal. However, such rotatability frequently complicates the pedal and cleat design. This is particularly true when a cleat is designed to be released by means of a rotary or twisting motion of the foot.
U.S. Pat. No. 4,686,867 to Bernard et al. is an example of clipless pedal designed to enhance pedaling efficiency. A bicycle pedal has a somewhat triangularly shaped pedal body which revolves about a pedal axis. A triangular cleat is connected rigidly to the cyclist's shoe and is designed to be inserted into a recess in the pedal body. The interface surface of the cleat is contoured to complement the contour of the curved outsole. Such a requirement for contouring makes it difficult to secure the cleat to the outsole in an off-center and stable manner. Having a rigid connection between the cleat and the shoe is also disadvantageous because any lateral or twisting movement of the shoe starts to disengage the cleat from the pedal. Therefore the cyclist must try to maintain his foot in a stationary alignment to keep the cleat in the fully engaged position on the pedal. As mentioned above, stresses on the ankle and knee joints thus can occur.
U.S. Pat. No. 4,815,333 to Sampson discloses an integrated bicycle pedal system with self-centering and lateral release capabilities which permits a limited degree of rotatability between the cleat and pedal during pedaling motion. The system consists of a cleat rigidly attached to the cyclist's shoe having two downward projections. These projections feature arcuate tracts for matingly engaging the cleat to a pedal body. The pedal body contains a biasing mechanism centered in the back of the pedal body. The cleat and the pedal body are configured so that the cleat rotates within a channel in the pedal body. The channel is designed to re-center the cleat in its optimum or central position after encountering torsional shocks or other motions. This re-centering capability is provided by the biasing mechanism which becomes increasingly compressed as the cleat is moved further from the central position. The centering function is provided by the spring used for securing the cleat to the pedal, so that the spring must have a high spring rate. Thus, although the cleat may be rotated without partially disengaging the cleat from the pedal, the cyclist will feel the effect of the biasing mechanism biasing the foot back toward the central position. Such a strong biasing force defeats the purpose of allowing limited cleat rotatability since stress is still placed on the ankle and knee joints.
The prior art fails to contemplate a cycling shoe and cleat wherein the cleat can be stably supported on a flat surface in an off-center position and wherein the cleat can be pivotally connected to the outsole in a manner which allows the cyclist to move his foot and the shoe without either partially disengaging the cleat from the pedal or encountering a biasing force from a biasing mechanism sufficient to create discomfort.